Fields of view (fields of vision) are legally prescribed (defined) for different types of motor vehicles, such as e.g., motorcycles, motor vehicles for transporting passengers, motor vehicles for transporting goods, etc. The fields of view must be provided by a device for indirect viewing, conventionally a mirror, and must be viewable permanently (continuously) and reliably at all times by a driver sitting in the driver's seat of the vehicle using the device for indirect viewing. Specific fields of view have been prescribed or defined by various countries, organizations and/or standards-setting bodies. For example, fields of view (vision) for rear-view mirrors, which must be viewable by the driver in a permanent an/or continuous and reliable manner, are legally prescribed in UN/ECE Regulation No. 46 for the European region.
For commercial vehicles, such as e.g., trucks or delivery vehicles, a primary (main) mirror is currently provided on each of the driver's side and the passenger's side as a device for indirect viewing. Using the primary (main) mirror, the vehicle driver can see a level (flat) and horizontal part of the road surface of a certain width that extends from a stipulated distance behind the vehicle driver's eye (ocular) points back to the horizon behind the vehicle. In addition, a narrower band of the road surface must also be viewable using this mirror, which band begins a shorter distance behind the driver's eye (ocular) points. Such legally-prescribed areas, which must be viewable permanently and at all times by the driver with the use of the devices for indirect viewing, will be designated as “fields of view (vision)”. The area in the vicinity of the vehicle that is legally prescribed or required to be viewable using the primary mirror will be designated hereinafter as the “field of view of the primary (main) mirror.” Such an area is also defined as field of view II (Class II) in UN/ECE Regulation No. 46.
In addition to these primary (main) mirrors, fields of view (vision), which are reproduced (shown or depicted) by wide-angle mirrors, are required to be viewable on both sides of the commercial vehicle. An area behind the eye (ocular) points of the driver is viewed with the wide-angle mirrors; this area is wider than the area that must be viewable in the primary mirrors, but it only extends a limited length along the vehicle—not to the horizon as is the case with the field of view of the primary (main) mirror. This area, the area viewable in the wide-angle mirrors, is defined as field of view IV (Class IV) in UN/ECE Regulation No. 46.
Various organizations may establish legally required fields of view for a main mirror. Currently, according to the field of view of Class II of UN/ECE Regulation No. 46, the field of vision of the exterior rear-view mirror on the driver's side and the exterior rear-view mirror on the passenger's side must allow the driver to see at least a 4 m wide, flat, horizontal portion of the road. This road portion is bounded on one side by a plane that a) is parallel to the median longitudinal vertical plane of the vehicle, b) passes through the outermost point of the vehicle on the driver's side and the passenger's side of the vehicle, respectively, and c) extends from a location 20 m behind the driver's eye (ocular points) to the horizon. In addition, a 1 m wide portion of the road must be visible to the driver in an area that is bounded by a plane a) parallel to the median longitudinal vertical plane of the vehicle, b) passing through the outermost point of the vehicle and c) extending from a location 4 m behind a vertical plane passing through the driver's eye (ocular points). In other words, the primary mirror must enable the driver to see a long wide portion of the road relatively far from the driver and a shorter, narrower portion of the road that is closer to the driver.
Various organizations may establish legally required fields of view for a wide-angle mirror. For example, Class IV of UN/ECE Regulation No. 46 defines a field of vision of the “wide-angle” exterior mirror on the driver's side and the “wide-angle” exterior mirror on the passenger's side. This wide angle field of view must allow the driver to see at least a 15 m wide, flat, horizontal portion of the road, that is bounded by a plane a) parallel to the median longitudinal vertical plane of the vehicle, b) passing through the outermost point of the vehicle on the driver's side and the passenger's side of the vehicle, respectively, and c) extending from a location at least 10 m to 25 m behind the driver's eye (ocular points). In addition, a 4.5 m portion of the road must be visible to the driver in an area that is bounded by a plane a) parallel to the median longitudinal vertical plane of the vehicle, b) passing through the outermost point of the vehicle, and c) extending from a point (location) 1.5 m behind a vertical plane passing through the driver's eye (ocular points).
Despite the use of prescribed mirrors or devices for indirect viewing (vision), however, it may be very difficult or nearly impossible for a vehicle driver to adequately keep accident-critical (accident-prone) areas around a commercial vehicle in view. In addition, the presence of multiple mirrors on typical vehicles makes it harder for the driver to keep all mirrors in view at the same time. The reproduction (depiction) of the fields of view using mirrors also has the consequence of an influence of the mirrors on the airflow around the vehicle.
With commercial vehicles such as trucks, buses, etc., the viewability on the driver's side is critical. Obstacles and other vehicles are often difficult to quickly and accurately identify in a mirror because, despite the specifications of legally-prescribed fields of view, relatively large blind spots still exist. The orientation of the driver relative to the multiple devices for indirect viewing changes as the driver moves his head and/or shifts his position in his seat, and this increases the likelihood that obstacles will be overlooked, in particular while turning or changing lanes, even though they are reproduced (shown) in the device for indirect viewing (and would be visible to the driver if his head were positioned in an ideal position). Accidents are thus frequently caused by the fact that drivers of commercial vehicles do not have sufficient viewability into lateral areas of the vehicle, in particular into the one or more blind spots, which are lateral areas adjacent to the vehicle. Even using the external mirrors described above, these lateral areas (the blind spots) are only barely visible by the driver, or are not visible at all.
It is becoming increasingly common to consider using camera systems or image capture systems as devices for indirect viewing, either in addition to conventional mirrors or as replacements therefor. In such camera systems or image capture systems an image capture unit continuously senses an image. The (video-) data sensed by the image capture unit are transmitted, e.g., using a computing unit, to a reproducing (display) device located in the driver's cabin. Optional further processing may be performed on the image before it is displayed. The reproducing (display) device depicts the corresponding legally-required field of view or a plurality of fields of view and optionally supplemental information, such as e.g., collision indications, distances and the like, for the area around the vehicle in a manner that is permanent (continuous) and viewable at all times by the driver.
DE 10 2011 010 624 A1 (corresponding to U.S. 2012/0200664) discloses a display device for legally-prescribed fields of view in a driver's cabin of a commercial vehicle. The display device includes at least one display adapted to display at least two of the legally-prescribed fields of view, permanently and in real time, on the display unit in the driver's cabin.
A camera unit and a device for monitoring a vehicle's surroundings are disclosed by DE 10 2004 043 257 B4 (corresponding to U.S. US 2005/083427). In this system a change of the image height with respect to a change of the image angle at a peripheral portion of the image is greater than in a center portion of the image.
It is also known to sense (capture) each of multiple legally-prescribed fields of view of a commercial vehicle using separate image capture units, respectively. In this case the image capture units are each aligned such that their optical axes, respectively, extend substantially through the centers of each of the sensed (captured) fields of view. The area of the image captured by the image capture unit has the highest reproduction quality at the optical axis, and the distortion, i.e. the optical distortion, increases with increasing distance from the optical axis.
Different requirements with respect to distortion are also placed on the image capture units for sensing (capturing) different legally-prescribed fields of view. For example, a first field of view must have only minimal distortion, whereas the distortion of a second field of view is less critical and thus it can be more distorted.
Furthermore, it is known to sense (capture) more than one legally-prescribed field of view using only one image capture unit. In this case the optical axis extends centrally through the viewing area captured by the image capture unit. However, this can lead to a distortion in each of the respective co-captured fields of view, because these co-captured fields of view do not necessarily lie in the central area.